There's a broad group of problems with the player's capsule fitting through Daggerfall's (rather poorly constructed) architecture, or being stuck on one-sided polygons left sticking up through the environment.

I have some ideas to resolve or minimise these problems over time, and will address when I'm ready. Until then, player's will just need to crouch.

The "teleport" console command while aiming crosshair at an open bit of ground is another way to bypass certain sticky spots.

I've implemented a fix for this now. Player will simply dip their head briefly when going under low doorways, like a very tall person ducking to go through doors. It's fairly smooth, although some visible "bounce" might be apparent.

Seems to work quite well, although there's bound to be some tuning needed later.